Re: [PATCH v2 2/2] exfat: check if cluster num is valid

Tadeusz Struk
2022-05-16T14:51:39Z

On 5/15/22 07:52, Sungjong Seo wrote:
>> Syzbot reported slab-out-of-bounds read in exfat_clear_bitmap.
>> This was triggered by reproducer calling truncute with size 0, which
>> causes the following trace:
>>
>> BUG: KASAN: slab-out-of-bounds in exfat_clear_bitmap+0x147/0x490
>> fs/exfat/balloc.c:174 Read of size 8 at addr ffff888115aa9508 by task syz-
>> executor251/365
>>
>> Call Trace:
>> __dump_stack lib/dump_stack.c:77 [inline] dump_stack_lvl+0x1e2/0x24b
>> lib/dump_stack.c:118
>> print_address_description+0x81/0x3c0 mm/kasan/report.c:233
>> __kasan_report mm/kasan/report.c:419 [inline]
>> kasan_report+0x1a4/0x1f0 mm/kasan/report.c:436
>> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
>> exfat_clear_bitmap+0x147/0x490 fs/exfat/balloc.c:174
>> exfat_free_cluster+0x25a/0x4a0 fs/exfat/fatent.c:181
>> __exfat_truncate+0x99e/0xe00 fs/exfat/file.c:217
>> exfat_truncate+0x11b/0x4f0 fs/exfat/file.c:243
>> exfat_setattr+0xa03/0xd40 fs/exfat/file.c:339
>> notify_change+0xb76/0xe10 fs/attr.c:336
>> do_truncate+0x1ea/0x2d0 fs/open.c:65
>>
>> Add checks to validate if cluster number is within valid range in
>> exfat_clear_bitmap() and exfat_set_bitmap()
>>
>> Cc: Namjae Jeon<linkinjeon@kernel.org>
>> Cc: Sungjong Seo<sj1557.seo@samsung.com>
>> Cc:linux-fsdevel@vger.kernel.org
>> Cc:stable@vger.kernel.org
>> Cc:linux-kernel@vger.kernel.org
>>
>> Link:https://protect2.fireeye.com/v1/url?k=24a746d8-45dcec51-24a6cd97-
>> 74fe48600034-8e4653a49a463f3c&q=1&e=0efc824d-6463-4253-9cd7-
>> ce3199dbf513&u=https%3A%2F%2Fsyzkaller.appspot.com%2Fbug%3Fid%3D50381fc738
>> 21ecae743b8cf24b4c9a04776f767c
>> Reported-by:syzbot+a4087e40b9c13aad7892@syzkaller.appspotmail.com
>> Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
>> Signed-off-by: Tadeusz Struk<tadeusz.struk@linaro.org>
> Looks good.
> And it seems that WARN_ON() is no longer needed.

Right. Do you want me to send a follow up patch that drops the WARN_ONs?

> Reviewed-by: Sungjong Seo<sj1557.seo@samsung.com>
>

Thank you.

--
Thanks,
Tadeusz